Zion Williamson may be done at Duke, but the top NBA prospect dished out one final assist before leaving.

Duke athletic department employee Nolan Elingburg and his wife, Danielle, recruited Williamson to facilitate their Blue Devils-themed gender reveal before he heads to the NBA.

After the pair announced they were expecting a baby, Williamson did what he does best and dunked a miniature ball that burst open with coloured confetti, which revealed a boy.

Williamson – projected to be the number one pick in this year's NBA Draft – declared via Instagram on Monday.

"I just want to say thank you. Thank you for making this season a dream for me," the 18-year-old star wrote. "I want to thank God, Coach K [Mike Krzyzewski], the assistant coaches, my family, my team-mates and all the friends I've made at Duke.

"Thank you for making this year the best year of my life. I don't think I can put it into words how special this year was."

Williamson averaged 22.6 points, 8.9 rebounds, 2.1 assists, 2.1 steals and 1.8 blocks for Duke last season. The 6-7 forward racked up plenty of accolades, earning ACC Player of the Year, ACC Rookie of the Year, the Naismith Award and the Wooden Award, among others.